1. Field of the Invention
The present invention relates to a three axis inertial measurement unit, and more particularly, to a compact, robust, and reliable three axis inertial measurement unit having a gyroscopic rotational rate sensor and a linear accelerometer.
2. Description of Related Art
Inertial measurement units (IMU) are known in the art and have been used in a wide variety of applications. For example, IMUs are commonly used in inertial guidance and navigation systems for all types of vehicles, in particular aircraft and spacecraft. Inertial navigation has the advantage of not being dependent on an external point of reference. Navigation is accomplished by sensing the motion of the vehicle and calculating the change in position with respect to an initial position.
A typical IMU consists of three equal modules, each including a gyroscopic rotational rate sensor, a linear accelerometer, and associated electronics. Each module is typically oriented on a cube or a similar structure to provide inertial measurements along one of three orthogonal axes, with the gyroscopic rotational rate sensors providing information regarding rotation of the unit and the accelerometers providing information concerning linear movement of the unit. In this way, the IMU is able to determine the position of the vehicle with respect to the vehicle's initial position to aid in guidance, navigation, and control of the vehicle.
Three axis inertial measurement units as described above have been used extensively in aerospace applications. Traditionally, such IMUs included conventional spinning mass gyroscopes and large mechanical accelerometers. However, most current IMUs utilize microelectromechanical systems (MEMS) devices. Current technologies using MEMS devices encapsulate the accelerometer, gyroscope, and associated electronics into individual packages. These packages are typically soldered to a circuit board, which is then mounted on one plane of an orthogonal assembly, such as a face of a cube. Electrical connections are made with wires and the circuit card assembly is attached to the orthogonal structure with conventional fasteners. These connections and fasteners increase the amount of space needed to house the complete IMU assembly and are prone to failure from fatigue.
Accordingly, there is a need in the art for an inertial measurement unit that is robust and compact and that will reduce the likelihood of failure of electrical connections.